104 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 19 30 



(a) Reductiort> of observations. — The observers in the field at 

 Montezuma, Chile, completely reduce their measurements according 

 to a definitive system adopted several years ago. Telegrams in code 

 arriving daily from Montezuma are decoded and furnished about 24 

 hours after observing to the United States Weather Bureau, which 

 publishes the solar constant values on the Washington daily weather 

 map. It is planned to include these results also in a broadcast of 

 miscellaneous geophysical data to begin in July, 1930, under the 

 auspices of Science Service. 



The variations of solar radiation seldom range beyond 3 per cent, 

 yet, as will appear below, they seem to produce important weather 

 changes even when as small as 0.5 per cent. It is only at high-altitude 

 stations under very tranquil sky conditions that results of sufficient 

 accuracy to display these small solar variations are to be obtained. 

 Although visibly excellent, our station at Table Mountain, Calif, 

 (longitude 117° 41' W., latitude 34° 22' N., altitude 7,500 feet), as 

 yet fails to give results of equal consistency to those of the station 

 of Montezuma. A thorough rereduction of all the Table Mountain 

 observations, 1925 to 1930, has been completed, with great labor, 

 during the past fiscal year. But it is disappointing. Fluctuations 

 too evidently produced by the haziness or humidity of the atmosphere 

 still are found occasionally in magnitudes of the order of 2 per cent. 

 Accordingly, a new method of reduction designed to more effectively 

 allow for these atmospheric changes was being developed at the close 

 of the period covered by this report. Preliminary results by it seemed 

 more promising. Reduction of Mount Brukkaros observations is 

 being postponed until the success of this new method is tested for 

 Table Mountain. 



(6) Atmospheric ozone. — As stated in last year's report, one 

 troublesome feature of the Table Mountain work has but lately 

 come to light through the studies of Fowle and of Dobson. It ap- 

 pears that a variation of large percentage occurs in the quantity of 

 atmospheric ozone prevailing at very high levels above Table Moun- 

 tain. Fortunately only about one-fifth as much change of ozone 

 occurs above Montezuma. The change occurring above Table Moun- 

 tain is sufficient, if uncorrected for, to introduce nearly 1 per cent 

 change in the results on the solar constant of radiation, but the 

 corresponding effect at Montezuma is negligible. 



We were not aware of this source of error when the Table Moun- 

 tain station was first occupied. It was not until several years after 

 the work began that we introduced there Dobson's method of meas- 

 uring ozone. Hence, if ozone corrections to solar constant values 

 were to be made from 1925 on, daily, and not merely by averages, 

 as suggested in last year's report, it became necessary to discover a 



